Treatment of ferrous metals to produce a protective coating thereon



Patented Nov. 6, 19 28.

UNITED STATES PATENT OFFICE- FRANKLIN BLISS RINCK, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TREATMENT OI IERROUS METALS TO PRODUCE A PROTECTIVE COATING THEREON.

No Drawing.

This invention relates to the treatment of ferrous metals to produce a protective coating.

thereon, and more particularly'to improvements in the treatment of such materials by the method known as BowerBarifing.

The object of this invention is to produce in a relatively short time a heavy, smooth, durable protective coating of black iron oxide which will be very adherent to the metallic surface and which will render the metal upon which it is applied rustproof and non-corrosive.

In accordance with the general features of the invention, the parts to which the protective coating is to be applied are subjected to an oxidizing atmosphere of steam at a relatively high but constant or rising temperature and the oxidizing character of the at mosphere periodically increased. This is accomplished Ky the admission of steam and by decreasing the concentration of the hydrogen which isformed by the reaction of the steam and the iron. The reduction of hydrogen concentration may be accomplished by burning out the hydrogen by the admission of air or oxygen or by purging out the furnace with a neutral gas such as nitrogen. Since an excess of uncombined oxygen is not conducive to the production of a desirable coating, it is removed by any suitable meansif it is permitted to enter the treating furnace. This may be accomplished by introducing into the furnace a hydrocarbon which reacts chemically with the oxygen'in the furnace atmoshere. p Carbon dioxide may be substituted for steam as the oxidizing agent in the format-ion of the iron oxide coating in which case carbon monoxide is produced as a by product instead of hydrogen. Its concentration may be controlled in any of the ways above described.

The details of the process may vary depending upon the equipment which is employed. It is preferably to employ an electric furnace having a muflie which can be closed sufiicient- 1y tight so that a positive pressure can be maintained therein. When an electric-muflle furnace of this type, large enough to accommodate 800 pounds of parts is used, the details of the process may be carried on as follows:

The perm to be treated are loaded in a rack and inserted in the muflle when a thermocouple inside the muflle registers a temperature of approximately 1400 F., about Application filed October 17 1924. Serial No.,744,2 91.

pint of hydrocarbon oil being placed in a container in the mufile with the iron parts. When the charge is placed in the muflle of the furnace, the temperature as indicated by the thermocouple is lowered thereby. The temperature of the load of parts as indicated by the above mentioned thermocouple which is "in close proximity to them is gradually raised until they have reached approximately the origmal temperature of the mufile, when-a small amountof steam is admitted thereto. The amount of steam admitted may be controlled in any suitable maner, but good results may be obtained when of a turn on a steam needle valve is made, the pressure of the steam controlled by the valve being 90 pounds. The steam'is superheated before entering the mufile so that its temperature is practically equal to the temperature of the mufile before it is finally introduced therein and during the process the amount of steam entering the mufiie is gradually increased. More specifically, in 10 minutes after first turning on the steam, the needle valve is advanced to of a turn and at the end of another 10 minutes to 4 of a. turn. ,This latter condition is maintained for another 20 minutes when the door of the muflle is opened to permit the hydrogen in the muflle to burn. A small amount of hydrocarbon oil, 4 pint when 800 pounds of parts is being treated, is again placed in the muflle of the furnace and the door immediately closed. During this time the steam is retained in the mufile and the parts are kept at a'temperature of about 142O F. which is the normal operating temperature of the furnace. At this temperature the hydrocarbon oil is vaporized and the at mosphere becomes one of mixed steam and vaporous hydrocarbon. The parts are allowed to remain for about 40 minutes in this atmosphere and are then withdrawn.

An oxide coating produced in this manner is smooth, very adherent, and entirely lacking in such defects as cracks, pin holes and discolorations.

What is claimed is:

1. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in subjecting said metal to an oxidizing atmosphere at a temperature which is not appreciably lowered during the process, and simultaneously therewith increasing the oxidizing character of said atmosphere.

2. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in subjecting said metal to an oxidizing atmosphere and maintaining the temperature thereof substantially constant during the process to avoid soaking the metal for an appreciable length of time at more than one temperature.

3. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in initially subjecting said metal to an oxidizing atmosphere at a predetermined temperature, maintaining the temperature substantially constant when a predetermined intensity is reached, and simultaneously therewith removing hydrogen from the oxidizing atmosphere.

4. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in subjecting said metal to an oxidizing atmosphere of steam, and gradually increasing the amount of said steam in said oxidizing atmosphere.

5. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in subjecting said metal to an oxidizing atmosphere of super-heated steam, gradually increasing the amount of said steam in said oxidizing atmosphere, and simultaneously therewith decreasing the amount of hydrogen in said oxidizing atmosphere.

6. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in initially subjecting said metal to an oxidizing atmosphere of super-heated steam at an elevated temperature, maintaining the temperature constant when a predetermined intensity has been reached, and simultaneously therewith reducing the amount of hydrogen in said oxidizing atmosphere.

7. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in subjecting said metal to an oxidizing atmosphere of steam. and simultaneously reducing the hydrogen concentration, increasing the amount of said steam and introducing hydrocarbon into said oxidizing atmosphere while said metal is being subjected thereto.

8. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists inheating said metal in an air tight container in the presence of steam, gradually increasing the amountof steam in the contain-' er, removing the uncombined hydrogen therefrom, and introducing a hydrocarbon oil.

9. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in heating said metal in an air tight container in the presence of steam, gradually increasing the amount of steam in the container, removing the uncombined hy-v drogen therefrom, and subjecting the metal to an atmosphere of steam and vaporous hydrocarbon.

10. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in subjecting said metal to it gradually increasing amount of super-heated steam in a container. and introducing hydrocarbon oil into the container.

11. The treatment of a ferrous metal to produce a protective oxide coating thereon, which consists in subjecting said metal in a container to a gradually increasing amount of steam and simultaneously decreasing the hydrogen content, and introducing hydrocarbon oil into the container.

12. The process of treating ferrous metal to render it rust-proof or non-corrosive,

which consists in subjecting the metal im-- mediately to an elevated temperature, progressively introducing an oxidizing medium, and contemporaneously therewith reducing the hydrogen content in the resulting oxidizing atmosphere.

13. The process of treating ferrous metal to render it rust-proof or non-corrosive, which consists in subjecting the metal immediately to an elevated temperature, progressively introducing an oxidizing medium in increasing amounts, and neutralizing the hydrogen content of the resulting oxidizing atmosphere.

14. The process of treating ferrous metal to render it rust-proof or non-corrosive, which consists in subjecting the metal immediatelv to an elevated temperature which is maintained substantially constant throughout the process, progressively introducing in increasing amounts an oxidizing medium, and contemporaneously therewith reducing the hydrogen content in the resulting oxidizing atmosphere.

In witness whereof, I hereuntosubscribe my name this 29 day of September A. D.,

FRANKLIN BLISS RINCK. 

